2020-06-28 22:54:42

by Tomas Winkler

[permalink] [raw]
Subject: [char-misc-next] mei: bus: don't clean driver pointer

From: Alexander Usyskin <[email protected]>

It's not needed to set driver to NULL in mei_cl_device_remove()
which is bus_type remove() handler as this is done anyway
in __device_release_driver().

Actually this is causing an endless loop in driver_detach()
on ubuntu patched kernel, while removing (rmmod) the mei_hdcp module.
The reason list_empty(&drv->p->klist_devices.k_list) is always not-empty.
as the check is always true in __device_release_driver()
if (dev->driver != drv)
return;

The non upstream patch is causing this behavior, titled:
'vfio -- release device lock before userspace requests'

Nevertheless the fix is correct also for the upstream.

Link: https://patchwork.ozlabs.org/project/ubuntu-kernel/patch/[email protected]/
Cc: <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Signed-off-by: Alexander Usyskin <[email protected]>
Signed-off-by: Tomas Winkler <[email protected]>
---
drivers/misc/mei/bus.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 8d468e0a950a..f476dbc7252b 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -745,9 +745,8 @@ static int mei_cl_device_remove(struct device *dev)

mei_cl_bus_module_put(cldev);
module_put(THIS_MODULE);
- dev->driver = NULL;
- return ret;

+ return ret;
}

static ssize_t name_show(struct device *dev, struct device_attribute *a,
--
2.25.4